The use of blood and blood products is extremely important in the treatment of many patients in serious or crisis situtations. The value of these materials, and particularly whole blood, has served to emphasize the problems in providing them in all appropriate circumstances. The use of blood requires storing of an adequate supply for all potential emergencies and careful crossmatching before use. In addition, infusion of blood still increases the risk of infections and immunological reactions. A blood substitute could aleviate many of these problems. Certain fluorinated hydrocarbons and emulsions based on fluorinated hydrocarbons have been proposed as blood substitutes but these have not been entirely satisfactory. What is proposed here is to investigate pyridoxalated hemoglobin crosslinked with various bifunctional reagents as the base for a blood substitute. The product would have a long shelf life (at room temperature), have the proper oxygen affinity and deposit parameters, osmotic balance, and we both immunologically bland and sterile.